Medical delivery catheters are well known in the art of minimally invasive surgery for introduction of fluids and devices to sites inside a patient's body. A well-established technique, known as “long wire guide,” for guiding a delivery catheter to a target site in a patient body includes: (1) positioning a wire guide along a desired path to the target site; (2) retaining a proximal portion of the wire guide outside the body; (3) threading the delivery catheter, which has a wire guide lumen throughout its length, onto the proximal end of the wire guide; and (4) advancing the catheter along the wire guide to the treatment site.
One example of a desired path to a target site is the passage through a working lumen or channel of an endoscope to a biliary duct in a. gastroenterological application. Another example of a desired path is through an endovascular lumen to an occluded coronary artery in a cardiological application. The delivery catheter may have a treatment device such as a stent or fluid-inflatable balloon disposed at its distal end for deployment at a target site (e.g., an occluded biliary duct or coronary artery). The catheter may also have a tool such as a cutting wire or cutting needle disposed at or near its distal end (e.g., a papillotome, sphincterotome, etc.), or the catheter may have an aperture for the delivery of a fluid through a second lumen (e.g., radio-opaque fluid for contrast fluoroscopy, adhesive or gelling agent for delivery to a target site, etc.).
Procedures that employ wire guides often require exchange of treatment appliances. For example, a balloon catheter may be replaced with a stent deployment catheter. In a typical application of such a procedure, a balloon catheter is directed to the site of a stenosis (e.g. in an artery, biliary duct, or other body lumen) as described above. Fluid is then used to inflate the balloon so as to dilate the stenosis. Some procedures are effectively concluded at this point. However, many procedures follow dilation of the stenotic stricture with the placement of a stent to maintain patency of the re-opened lumen. This requires that the balloon catheter be withdrawn to allow introduction of a stent-deployment catheter. It is preferable that the wire guide remain in place for guidance of the stent-deployment catheter without having to re-navigate the wire guide back into to the newly re-opened lumen.
In order to prevent undesired displacement of the wire guide, any exchange of long wire guide catheters requires that the proximal portion of the wire guide extending out of the patient's body (or endoscope, depending on the entry point for the desired path to the target site) must be longer than the catheter being “exchanged out” so that control of the wire guide may be maintained as the catheter is being removed. Likewise, the wire guide must be grasped while the entire catheter being “exchanged in” is threaded onto it and directed along the desired path to the target site. In other words, for the operating physician and assistant to be able to hold the wire guide in place while removing one catheter for replacement with another, each of the catheters must be shorter than the portion of the wire guide that is exposed outside the patient's body (and, if used, outside the endoscope). Put another way, the wire guide must be about twice as long as a catheter that is being used over that wire guide. Additionally, in the case of gastrointestinal endoscopy, even more wire guide length is necessary. This is because the shaft of the endoscope through which the wire guide and catheters are placed must have a length outside the body for manipulation and control, and the catheter itself must have some additional length outside of the endoscope for the same reason. As those skilled in the art will appreciate, wire guides having the necessary “exchange length” are cumbersome and difficult to prevent from becoming contaminated.
An alternative technique for guiding a delivery catheter to a target site in a patient body utilizes catheters having a relatively short wire guide lumen in catheter systems commonly referred to as “rapid exchange,” “short wire guide,” or “monorail” systems. In such systems, the wire guide lumen extends only from a first lumen opening spaced a short distance from the distal end of the catheter to a second lumen opening at or near the distal end of the catheter. As a result, the only lumenal contact between the catheter's wire guide lumen and the wire guide itself is the relatively short distance between the first and second lumen openings. Several known advantages are conferred by this configuration. For example, the portion of the wire guide outside the patient's body may be significantly shorter than that needed for the “long wire configuration.” This is because only the wire guide lumen portion of the catheter is threaded onto the wire guide before directing the catheter through the desired path (e.g., a working lumen of an endoscope, an endolumenal passage, etc.) to the target site.
By way of illustration, the prior art pictured in FIGS. 1A and 1B illustrate the distal ends of two different types of typical catheters. FIG. 1A shows the distal end of a prior art long-wire catheter shaft 100 with a wire guide 102 disposed in a lumen 104. The lumen 104 extends substantially to the proximal end of the catheter shaft 100. (Note: The wire guides illustrated throughout this specification are drawn to illustrate the concepts being described and may not be shown to scale; preferred wire guides typically have an outer diameter that is nearly the same as the inner diameter of catheter lumens through which they are passed.)
FIG. 1B shows the distal end of a prior art short-wire catheter shaft 110 with a side port aperture 111 and a wire guide 112 disposed in a lumen 114. The length of the lumen 114 used by the wire guide, and consequently the exchange length of the catheter 110, is substantially shorter than that of the catheter 100 shown in FIG. 1A. In addition to a shorter exchange length, the catheter 110 (FIG. 1B) has a reduced surface contact between the wire guide and catheter lumen that results in a reduced friction between the two. This can result in an eased threading and exchange process by reducing the time and space needed for catheter exchange. This economy of time and space is advantageous for minimally invasive surgeries by reducing the likelihood of contamination and reducing the total time and stress of completing surgical procedures.
In certain rapid exchange catheter configurations, the wire guide lumen is open to a side port aperture in the side of the catheter between its proximal and distal ends. In one such configuration, the wire guide lumen only extends from the side port aperture to an opening at the distal end. The rapid exchange catheter illustrated in FIG. 1B is one example of this catheter type.
In another type of rapid exchange catheter configuration, the wire guide lumen extends through the length of the catheter from near its proximal end to its distal end. A side port aperture between the proximal and distal ends opens into the wire guide lumen. This side port aperture allows the catheter to be used in a short wire guide configuration, while the full-length wire guide lumen allows the catheter to be used in a long wire guide configuration. This wire guide lumen configuration is referred to as “convertible” or “dual use.” An example of this type of catheter is illustrated in FIG. 1C, which shows a “convertible” catheter shaft 120 with a wire guide 122 disposed through a side port aperture 121 in a distal portion thereof and into a wire guide lumen 124. Specifically, a wire guide 122 may extend through substantially the entire length of the wire guide lumen 124, or the wire guide may extend only through a portion of the lumen 124 between the distal end and the side port aperture 121 (as is illustrated in FIG. 1C).
One common method of producing a side port aperture is by “skiving”—passing a cutter across a catheter surface in a direction transverse to the catheter's longitudinal axis. As shown in the perspective view of a catheter 180 in FIG. 1D, when a semicircular or circular cutter is used to make such a transverse cut, the skived out portion forms a generally elliptical side port aperture 182 that is open to a first lumen 184, which extends generally parallel to the catheter's longitudinal axis. The side port aperture 182 is not open to a second lumen 186, which extends longitudinally through the portion of the catheter 180 opposite the aperture 182.
FIG. 1E shows a catheter 190, wherein the side port aperture 192 was made using an L-shaped cutter or multiple straight cuts to skive out a wedge-like portion of the catheter 190. When the catheter 192 is generally cylindrical, the shape of this wedge-like side port aperture most closely approximates an ungula of a right cylinder. The side port aperture 192 also exposes a longitudinal lumen 194.
While offering advantages as explained above, catheter configurations having side port apertures of the type shown illustrated in FIGS. 1D and 1E may be prone to undesirable flexure (e.g., excessive bending, kinking, twisting, or binding) in the region around the aperture. This may often be due to a lack of full columnar support in the region of the side port aperture. For example, and as illustrated in the catheter 195 shown in FIG. 1F, skiving or using other means to create a side port aperture 196 often removes more of the catheter wall than is strictly necessary to allow passage of a wire guide 197 into/out of a lumen 198.
Undesired flexure can have several negative consequences. For example, kinking or excessive flexure of the catheter may cause one or more lumens to be closed off—thereby preventing their use, or may cause a non-smooth edge to be formed adjacent the aperture that could cause damage (e.g., injure an endolumenal passage of a patient or damage the working channel of an endoscope through which the catheter shaft is being passed).
In addition, and as shown in FIG. 1G, a dual use configuration catheter may tend to allow a wire guide 132 being passed from one end through the length of a catheter 130 (particularly if the catheter is bent/curved while in place in the body of a patient being treated) inadvertently to pass out through the side port aperture 131, rather than proceeding to the other end of the wire guide lumen 134. This presents an obvious problem in that a wire guide, to be useful, must exit the wire guide lumen of the catheter via the desired aperture (such as a desired end aperture or another side aperture).
Accordingly, there is a need for a side port aperture configuration that reduces undesirable flexure of the catheter shaft in the region near the side port aperture providing access into the lumen of the catheter. There is a further need for side port aperture that, in a dual use catheter, is configured such that a wire guide being directed from the proximal end through the wire guide lumen has a reduced likelihood of exiting out through the side port aperture.
There is also a need for a method of manufacturing a catheter having a side port aperture that permits greater precision and variety in the formation and configuration of the aperture than is possible with conventional methods.